Post-eq effects loop

In late 1975, Marshall introduced the "Master Volume" ("MV") series with the 100W 2203, followed in 1976 by the 50W 2204. This was an attempt to control the volume level of the amplifiers whilst maintaining the overdriven distortion tones that had become synonymous with the Marshall brand. In order to do this, Marshall designers connected the two input stages in series rather than parallel on the 2203, but not initially on the 2204, and modified the gain stage circuitry to preserve the tonal characteristics of the 'cranked Plexi' sound and converted the now obsolete second channel volume control to a Master Volume by wiring it between the preamp and EQ circuit. The 2204 followed suit in early 1977 and changed its preamp circuit to match the (then) more popular 2203.